The present invention relates to a method of killing field mice and the like in which the field mice are suffocated to death by the use of liquid nitrogen, and further relates to an apparatus for practicing the method.
The field mouse generally makes its burrow in mountain, forest, pasture, cultivated field and the like, the burrow having meandering horizontal holes 3-5 cm in diameter and 5-20 m in length and a few openings to the surface of the ground. The field mouse eats vegetables, grain and bark and root of trees. Particularly, in orchards in snowy districts field mice which have eaten all foods stored in their burrows before snow fall move out of the burrows for food, pass clearance formed between the ground surface and snow due to the heat of the ground and eat bark and root of fruit-trees, to thereby wither them and give serious damage to the farmers. Further, field mice cause large damage such as a great deal of stock feed being eaten and dangers such as gas leakage caused by gnawing holes through gas pipes, electric leak by eating away the insulation from electric wires, etc.
In order to prevent such damage caused by field mice there have been made various proposals, but satisfactory mouse-killing effects have not yet been produced by such proposals. For example, it is a common practice to put a mouse poison in passages and holes of field mice and kill the mice which eat the poison. However, the mouse poison has strong toxicity not only to field mice but also to the other living creatures and hence careful treatment is needed for the mouse poison. Further, there is no effect of the poison unless mice eat it. Thus, the mouse poison does not provide sufficiently efficient mouse-killing effect. There is another conventional method in which a poisonous liquid is injected into a burrow of field mice to thereby poison them to death, but this method provides a poisonous matter to trees and vegetables, so that they can be withered or their crop can be improper for food. The other disadvantage of this method is that field mice sense smell of the poisonous liquid and get away.